Abstract:
Phenol-soluble modulins (PSMs) are key virulence factors of S. aureus, and they comprise the structural scaffold of biofilm as they self-assemble into functional amyloids. They have been shown to interact with cell membranes as they display toxicity towards human cells through cell lysis, with αPSM3 being the most cytotoxic. In addition to causing cell lysis in mammalian cells, PSMs have also been shown to interact with bacterial cell membranes through antimicrobial effects. Here, we present a study on the effects of lipid bilayers on the aggregation mechanism of αPSM using chemical kinetics to study the effects of lipid vesicles on the aggregation kinetics and using circular dichroism (CD) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) to investigate the corresponding secondary structure of the aggregates. We found that the effects of lipid bilayers on αPSM aggregation were not homogeneous between lipid type and αPSM peptides, although none of the lipids caused changes in the dominating aggregation mechanism. In the case of αPSM3, all types of lipids slowed down aggregation to a varying degree, with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) having the most pronounced effect. For αPSM1, lipids had opposite effects, where DOPC decelerated aggregation and lipopolysaccharide (LPS) accelerated the aggregation, while 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DOPG) had no effect. For αPSM4, both DOPG and LPS accelerated the aggregation, but only at high concentration, while DOPC showed no effect. None of the lipids was capable of inducing aggregation of αPSM2. Our data reveal a complex interaction pattern between PSMs peptides and lipid bilayers that causes changes in the aggregation kinetics by affecting different kinetic parameters along with only subtle changes in morphology.
摘要:
酚溶性调节蛋白(PSMs)是金黄色葡萄球菌的关键毒力因子,它们包含生物膜的结构支架,因为它们自组装成功能性淀粉样蛋白。它们已被证明与细胞膜相互作用,因为它们通过细胞裂解对人细胞显示毒性,αPSM3细胞毒性最强。除了在哺乳动物细胞中引起细胞裂解,PSM也已显示通过抗微生物作用与细菌细胞膜相互作用。这里,我们使用化学动力学研究脂质双层对αPSM聚集机制的影响,以研究脂质囊泡对聚集动力学的影响,并使用圆二色谱(CD)光谱,傅里叶变换红外(FTIR)光谱和透射电子显微镜(TEM)研究了聚集体的相应二级结构。我们发现脂质双层对αPSM聚集的影响在脂质类型和αPSM肽之间不均匀,尽管没有脂质引起主要聚集机制的变化。在αPSM3的情况下,所有类型的脂质在不同程度上减缓了聚集,1,2-二油酰基-sn-甘油-3-磷酸胆碱(DOPC)具有最明显的效果。对于αPSM1,脂质具有相反的作用,DOPC减缓聚集,脂多糖(LPS)加速聚集,而1,2-二油酰基-sn-甘油-3-磷酸-消旋-(1-甘油)(DOPG)没有影响。对于αPSM4,DOPG和LPS都加速了聚集,但只有在高浓度下,而DOPC没有效果。没有一种脂质能够诱导αPSM2的聚集。我们的数据揭示了PSM肽和脂质双层之间的复杂相互作用模式,该模式通过影响不同的动力学参数以及形态的细微变化而引起聚集动力学的变化。